Parkinson's Drugs Linked to Sex and Gambling Addictions

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Pathological gambling, hypersexuality and compulsive shopping are
some of the abnormal behaviors that are linked to the use of
certain drugs commonly used to treat Parkinson's disease,
according to a new study.

The findings are important because they mean that doctors and
patients should be wary of the drugs' side effects, according to
the study authors. But they also give researchers a better
understanding of
how abnormal behaviors develop in general, and how such
behaviors may be related to the brain receptor that is targeted
by the drug, the authors said.

"In our view, these medications should be used less frequently
and with great caution, paying close attention to possible
untoward effects on behavior and impulse
control," said Dr. Howard D. Weiss of Sinai Hospital of
Baltimore and Dr. Gregory M. Pontone of Johns Hopkins University
School of Medicine in Baltimore, Maryland, writing in an
editorial about the new study.

In the study, the researchers examined 1,580 reports of people in
the United States and 21 other countries experiencing
pathological gambling,
hypersexuality, compulsive shopping or other abnormal
behaviors after taking medication between 2003 and 2012. They
found that 710 of the cases occurred in people taking drugs
called dopamine receptor agonists, which are used to treat
Parkinson's disease, whereas the other 870 cases occurred in
people taking all of the other types of drugs combined.

The researchers determined that the proportion of such reports
was 277.6 times higher for people taking dopamine agonist
receptor drugs than those taking other drugs. [ 7
Bizarre Drug Side Effects ]

Dopamine is a neurotransmitter in the brain that normally helps
regulate movement, emotions and the feelings of pleasure. In
people with
Parkinson's disease, the brain cells that make dopamine die
over time. Dopamine receptor agonists are used to mimic the
function of the neurotransmitter.

The important step to take after the new findings is to introduce
warnings about the potential side effects of those drugs so that
doctors who prescribe them are aware of them, said study author
Thomas J. Moore, a senior scientist at the Institute for Safe
Medication Practices in Alexandria, Virginia.

"They [doctors and caregivers of Parkinson's patients] need to be
on the lookout for this kind of behavior" and understand it may
be linked to the use of medication, Moore told Live Science.

Of all the cases of abnormal behavior that were observed in the
people taking the drugs for Parkinson's disease, the majority
(410 cases) occurred in those who had been taking a dopamine
receptor agonist drug called pramipexole, which affects a
receptor called dopamine D3 receptor. And the drug that was
second-most commonly linked to such behaviors was ropinirole,
which also has a significant effect on the D3 receptor, according
to the study, published today (Oct. 20) in the journal JAMA
Internal Medicine

The researchers noted that in some cases, the people taking these
drugs had restless leg syndrome (not Parkinson's disease).

The new research may allow researchers to better understand how
abnormal behaviors develop, and how they may be related to the D3
receptor, Moore said. The D3 receptor has also been investigated
as a possible target for treatments for people with addictions,
the researchers wrote in the study.

In another
study, published in July 2011 in the journal Physiology &
Behavior, other researchers also found a link between behaviors
such as hypersexuality or excessive gambling and the use of the
two drugs that Moore found to be the most closely related to
abnormal behaviors in the new study.

Drugs for Parkinson's have been down this road before. In the
1960s, the introduction of the Parkinson's drug levodopa enabled
Parkinson's patients to “regain function and return to the
mainstream of life," Weiss and Pontone wrote.

Levodopa gets converted into
dopamine in the brain, said Weiss and Pontone, who were not
involved with the new research.

However, enthusiasm for that treatment was tempered when patients
taking it developed involuntary muscle movements, similar to
tics, and in rare cases also developing abnormal behaviors such
as hypersexuality, they wrote.

The newer class of Parkinson's drugs — the dopamine receptor
agonist drugs — act differently in the brain, Weiss and Pontone
wrote. Levodopa gets converted into dopamine in the brain, the
dopamine receptor agonist drugs just mimic the neurotransmitter's
effects.

It was known that the dopamine receptor agonist drugs caused side
effects such as hallucinations, psychosis and
excessive daytime sleepiness. But despite these effects, the
drugs remain widely used, and it is only recently that doctors
started recognizing a link between the use of those drugs and the
occurrence of impulse control disorders with symptoms such as
pathological gambling, hypersexuality and uncontrollable
spending, Weiss and Pontone wrote.

It is not surprising that it took a while for doctors to start
recognizing the link between the two, they wrote, as they did not
routinely inquire about the potentially behavior-altering effects
of the drugs.

"During an office visit, a patient is unlikely to spontaneously
mention, 'By the way, doctor, I lost $250,000 in casinos last
year, and I purchase $500 of lottery tickets every week' or 'I
spend all night on Internet pornography sites and am soliciting
prostitutes,'" Weiss and Pontone noted.

"In summary, physicians have overestimated the benefit and
underestimated the risks associated with the use of dopamine
receptor agonist drugs in patients with Parkinson disease," they
wrote.